A challenge in doing affordable but legal design work is finding a source for good free photographs. With a stock photo you pay based on how you are using the photo (and each time you want to use that photo). With a royalty-free photo you pay a set fee for the right to use that photo in just about any way and as often as you desire (google "royalty-free photos"). What I like is the totally free photo, which can costs you the time to download it and which you can use as you like (within reasonable limitations imposed by the site). Here are some of my favorite sources.
A disclaimer: I cannot guarantee that there are no offensive images to be found in these sites.
Sources of Totally Free Photos
http://office.microsoft.com/en-us/clipart/default.aspx (suggested by an anonymous commenter - thanks!)
There is no good way to know which of the images at http://images.google.com/ and http://flickr.com/ are in violation of copyright law and you're better off avoiding them. As you find other good sites, please let me know and I'll add them here.